For restaurants that are still offering indoor service — or that would like to do so in the near future — finding ways to mitigate the transmission of the SARS-CoV-2 virus is vital to their survival.

Filters and Air Purifiers

Before the pandemic, many restaurant owners were concerned with IAQ, but mainly as it related to customer comfort, which meant temperature and humidity were the top concerns, said Bob Bazzoli, refrigeration service manager at EMR Delaware Valley, which provides service, repairs, parts, and installation to the commercial kitchen service sector.

“Now, restaurant owners are seeing the advantages of more sophisticated air filtering and microbial, odor, and small particulate removal,” he said. “Most owners now are choosing to install slightly higher MERV rated filters and adding electronic or physical air scrubbers to further improve the indoor air.”

While the average cost to install better filters is minimal — only about 25% higher than standard filters — higher MERV filters can adversely affect the HVAC system if not applied correctly, said Bazzoli. That’s because the higher the MERV rating, the higher the resistance to flow of air circulation, which defeats the comfort level by slowing down air circulation and a unit’s efficiency to heat and cool. This, in turn, stresses the air handler.

Another option that restaurant owners are considering are electronic air purifiers, which are designed to reduce the particulates, odors, and microbial circulating in the conditioned space at a cost of about $0.05 per run/hour per unit, said Bazzoli.

“Initial cost for the equipment and proper installation can run between $1,000 and $1,340 per unit, making the initial cost rather prohibitive for some struggling COVID-hit customers, especially when there are several air handlers for the same location (the average 50-seat restaurant has four units),” he said. “Proper maintenance of air handlers is still important to the air quality, as well as extending the life of the purifier, but the new electronic units require no special care other than quarterly cleaning.”

Better Ventilation

In addition to properly maintaining air handling units (AHUs), increasing ventilation is another important tool that can be used to mitigate the spread of the SARS-CoV-2 virus. Even though restaurants generally have more air changes than typical retailers because of the ventilation associated with cooking operations, there may still be a need to increase the fresh air for dining room systems, depending upon the mechanical design, said Danny Miller, president of Transformative Wave, which offers ventilation solutions through the intelligent management of HVAC outside air levels.

“If a dedicated make-up air unit (MUA) is used, the HVAC units are less likely to be providing sufficient outside air to meet the recommendations of ASHRAE and the CDC, particularly for the dining room(s),” he said. “Another consideration is whether the HVAC units have economizers or fixed outside air dampers. The lack of working economizers makes it very difficult to improve the fresh air dynamics in any restaurant.”

The cost to improve the ventilation system in a restaurant is predicated on what HVAC equipment is currently in place, said Miller. For example, does the restaurant have economizers? Are the units eligible for high-efficiency filters? Is there a building management system (BMS) that provides control over outside air (OSA) damper positions and schedules?

“If economizers are present, the needed adjustments can be made manually, so the costs are associated with paying service providers and can be included as part of preventive maintenance visits,” he said. “The challenge is that these changes are not dynamic. Increased outside air generally comes with an energy penalty, which is where an investment in technology like Transformative Wave can provide a more intelligent approach that considers the impact on comfort and space pressure. Fortunately, as an energy efficiency solution, utility subsidies and funding mechanisms exist that can assist struggling operators with the cost.”

Investing in a better ventilation strategy may be warranted, given the indications that infected aerosols build up in concentration over time, similar to smoke or CO₂ levels, said Miller. This increases the risk of airborne transmission to patrons or staff, and the primary mechanism for dealing with this is dilution with fresh outside air.

“There are many competing demands being placed upon restaurant owners, and most businesses have suffered economically,” he said. “Our advice for restaurant owners is to avoid underestimating the central role of HVAC systems in public health. Invest in the service and repair of existing equipment and look at them as a whole system and not just individual appliances. Investigate enabling technology that will provide remote and intelligent control of the restaurant environment. Finally, stay abreast of the latest recommendations and science with the realization that they have and may continue to evolve.”

UV-C Solutions

When Lucas Turnbull, sales engineer in the Building System Solutions division of Thermosystems LLC in Elmhurst, Illinois, talks with restaurant owners about what they can do to mitigate the transmission of the SARS-CoV-2 virus, he advises them to follow ASHRAE’s guidance. This includes increasing outside air (OA) levels to the limit of space temperature and humidity control, increasing filtration to the limit of the existing HVAC fan motor, and keeping the relative humidity (RH) levels in indoor spaces at 40-60%, provided the building envelope can retain additional moisture.

UV-C SOLUTION: When working with restaurant owners to find solutions to mitigate the transmission of the SARS-CoV-2 virus, Thermosystems often ends up installing germicidal UV-C lights.

“We also take a deep dive into each building’s individual HVAC system and look for opportunities to install germicidal UV-C lights,” he said. “If the restaurant’s HVAC system does not lend itself to UV-C lights in a rooftop unit or central AHU, then we will look for opportunities to incorporate upper-room UV-C fixtures or other means of disinfecting room air.”

UV-C is medical-grade air disinfection that is recommended for reducing virus transmission by many different entities, including ASHRAE and the CDC. And, unlike higher MERV-rated filters, UV fixtures do not restrict airflow; in fact, they can boost airflow levels (lowering pressure drop) by continuously cleaning coils and removing microbial debris, said Daniel Jones, president and co-founder of UV Resources, which offers a variety of UV-C solutions. UV-C light has been shown to inactivate the genetic material in the SARS-CoV-2 virus, and when aerosolized, the virus is likely to be more susceptible to UV-C damage than other coronaviruses such as SARS-CoV-1 or MERS-CoV.

“Germicidal UV technology can be widely deployed in nearly all restaurant air handling equipment to mitigate the spread of COVID-19,” he said. “In terms of application hurdles, there aren’t many. For upper-room UV fixtures, the only consideration is a ceiling that is at least eight feet high and that the upper room area where the UV-C energy will be installed is free of obstructions (hanging televisions, signage, framing soffits, etc.) that might misdirect the UV energy.”

When it comes to specifying UV-C for a restaurant, contractors must understand that there are many factors that influence the sizing of airstream disinfection systems and that there is no one-size-fits-all scenario, said Jones.

DEMONSTRATED CARE: Restaurant owners/managers are using germicidal UV-C to not only reduce the potential spread of airborne diseases, but also to demonstrate to their customers that they have taken precautions to mitigate the spread of the coronavirus. Courtesy, UV Resources

“For example, the volume and velocity of air traveling through an HVAC system significantly impact the length of exposure to the germicidal wavelength (residence time) — a higher volume of air and/or higher velocity airstreams require greater UV intensity,” he explained. “Similarly, air temperature (cold air reduces the output of UV-C lamps); humidity (high RH decreases pathogen susceptibility to UV-C); and duct reflectivity all play a role in determining the amount of UV-C energy necessary in any given application. That’s why most installations are modeled by UV-C fixture manufacturers to help predict individual dosage levels.”

As far as cost is concerned, UV-C is relatively inexpensive to install and maintain, said Turnbull.

“Our upper-room UV-C device is as easy as installing a flat-screen TV and as expensive as operating a light,” he said. “As the system gets larger, the initial costs go up, but we do not see that as a negative. When we are installing larger systems, we have greater flexibility to place the UV-C fixtures where they will not only provide air disinfection, but also increase energy efficiency and decrease operating costs of the HVAC system.”

From a retrofit cost standpoint, Jones notes that UV is among the most affordable infection mitigation strategies, as upper-room germicidal fixtures can be installed at roughly $4.00 to $4.50 per square foot of treated area. Airstream UV disinfection systems for HVAC systems and duct runs commonly used for restaurant spaces have an installed price of roughly $0.25 to $0.30 per cfm, and local and federal subsidies may be available to help defray the cost further.

“Most restaurants implementing these fixtures focus on high traffic areas such as entry vestibules, waitress/hostess stands, restrooms, billiards/game areas, etc.,” he said. “The average UV equipment for an upper-room application can be purchased for less than $1,300/unit. For a 2,500-square-foot restaurant space (about 100 customer seats), the cost for an in-duct or airstream disinfection system would be less than $1,000.”

Whatever IAQ solution restaurant owners end up implementing, the best advice is to ask a professional for help, rather than trying to implement a DIY solution, said Don Jones, service manager at EMR Beltsville. He has seen an uptick in owners of single restaurants trying to come up with solutions themselves in order to save money, but in the long run, this could actually cost them more money and result in a higher utility bill.

“For example, we had a restaurant owner disable his makeup air unit and run the kitchen exhaust only. When questioned, he said he wanted to pull the air from the dining room where the virus may be,” said Don Jones. “Other customers have gone to their local home improvement store and purchased portable air cleaners with HEPA filters and put them in the lobbies of their restaurants/facilities. It’s a hard sell for most customers because their main focus is just surviving.”